You can't put a Camaro in your 401(k), but investing in rare cars can be more profitable than you might realize: Investment-grade autos increased their value by 457% in the last ten years, according to a report from Knight Frank. That's like multiplying your cash five-fold in just a decade.

Compare that with the boring old stock market, where 10-year returns are usually closer to 20% in a good decade. That big difference may explain why almost 10% of wealthy people's money is invested in alternative pleasure assets like art, wine and fancy cars.

Now, it's certainly tempting to try to look at how rich folks grow their money quickly, and try to follow suit. But before you go cashing out your emergency fund to stock up on brandy and Picassos, there are a few crucial things to know. For one, tangible assets tend to carry a lot of risk: If you're not lucky, you'll buy something that's hard to sell (aka illiquid), that's easily damaged or destroyed, or — if you're really unlucky — that turns out to be fake.

Investors typically mitigate risk with diversification, but those without a trust fund will have a hard time doing so across pleasure assets. Plus, funds offering diversified exposure to pleasure assets have only been around since 2006 or so, and are thus relatively untested.

Still interested in trying to make a quick buck from an investment in collectibles? Here's what you need to know.

Why you probably shouldn't invest in pleasure assets

Aside from upkeep and insurance, the main problem with pleasure-asset investing is the barrier to entry: You need a lot of money to even get started.

"In general the rule of thumb [for investment-grade art] is if you are or were represented by a big gallery or are in museums, there's a market," Rony More, founder and CEO of the gallery Art Please, said. "You're essentially no longer a 'penny stock.'"

It's true you can get lucky and discover a lesser-known artist right before their career takes off, but whether you'll choose a star or a dud can be a toss up, said More: "There are ways of investing in art in small amounts of money ... but with an emerging artist it's very difficult to know if that's going to appreciate because there's no track record."

A good deal of the art market is focused on a handful of key names, like Pablo Picasso, whose works fetch millions. Matt Dunham/AP

People buy investment art mostly on the basis of name, More said, with most money going to a handful of artists' work. And that investment-grade art will cost you, from the high ten-thousands on the low end — up to millions.

Wine is hardly any better in that regard; experts mostly agree that you'd need in excess of $12,000 to $15,000 to get started. Investment-grade wine is from the best regions, ages perfectly and receives praise from the best critics, said Karen MacNeil, author of the Wine Bible. That trifecta will also cost 'ya.

"If it's an $8 wine, there's a reason it's $8," MacNeil said. "What makes wine so mysterious is that much of what causes greatness is unknown, so we only know it empirically after a 40- or a 50-year track record."

Then again, some argue wine collecting could get easier as enthusiasts shift away from ultra-pricey choices: "People are looking for more value," said wine consultant Henry Mautner.

As for cars, the barrier of entry is higher. "Certain 'super cars' appreciate after they are released because, at times, as few as 5 or 10 of the cars will be produced in the world," Scott Chesrown, chief revenue officer at Vroom, an online dealership that sometimes sells rare cars, said. "For comparison, a mainstream car or truck could have 300,000-500,000 units produced in a year."

Supercars typically fetch hundreds of thousands of dollars at auction, if not more — not the kind of money people typically have lying around.

To even have a chance of appreciating, a car needs to be incredibly rare. Richard Drew/AP

Now, with all these caveats in mind, you might be totally turned off by the idea of investing in tangible collectibles. But there certainly can be upsides if you can afford the investment.

Why people invest in passion assets

The most adept of investors try to keep their passions in check, said Tsai Capital founder Christopher Tsai — one such investor who has amassed a famous collection of works by Chinese artist Ai Wei Wei.

"Back [in the mid-2000s], contemporary Chinese paintings by what are today considered some of the foremost names were selling for underneath $10,000," Tsai said. "Now, many of those paintings went to a million."

That's a huge appreciation in value that Tsai got to enjoy, though knowing exactly when a deal is smart can be tricky, he said.

"Every piece of art I buy I consider an investment," he said. "But I only buy art that I love. So the stars have to align. I might love a painting but feel it is overvalued, in which case I would pass."

Indeed, investing in stocks and investing in art is not as dissimilar as you'd think, Tsai said: "There are striking similarities between the two asset classes... We're looking for downside protection and upside potential. And the way to achieve that... is to build in a margin of safety with a purchase."

By margin of safety, Tsai is alluding to value investing, a popular style among investors like Warren Buffett. Value investing is the practice of buying a stock (or a painting, in this case) not so much because you think its value will grow, but because you think it's a bargain and is currently underpriced.

Of course, even that definition can be fairly subjective. And other art investors have shared different philosophies about and reasons for investing.

Tsai is known in the art world for being an early collector of the Chinese artist Ai Weiwei, whose pieces are now worth millions. Petr David Josek/AP

"It's not just about hanging something pretty, it's about capital appreciation," Mor said. "And what art provides ... is little to no correlation to the major indexes like the S&P 500."

In other words, art doesn't necessarily lose its value when the stock market does. The appraiser Michael Moses calculated that art had annual compound returns of about 9% in the last 60 years, comparable to the stock market. But art prices held steady during the financial crisis, and they actually fell in the subsequent rebound. A lack of correlation is a good thing for diversification.

Proponents of investing in classic cars also had a pragmatic case of their own. Christopher Bruno founded Rally Rd. to sell shares of stock in classic cars the same way you would a company. Unlike a company, Bruno said, a classic car can't declare bankruptcy; its price has a floor.

"Much of what we've seen in other asset classes, the risk profile is either zero or home run," Bruno said. "But with collectible assets like this, there's a bit more of a back stop. You can always take the car to auction. It gives you an interesting option."

Of course, there's a caveat here, too: Bloomberg's Kyle Stock raises a few compelling arguments against investing in cars, noting that only 3% of vintage cars actually sell at auction, for example.

Finally, it should go without saying that none of these investments make good choices if you haven't checked every other personal finance box first. You probably should not invest in art if you don't yet have an emergency fund, a maxed-out retirement account and plenty of other plain vanilla investments.

There's no denying that investing in pleasure assets might go mainstream; Bruno said he envisions one day letting customers buy small shares of a classic car for as little as $30 or $40.

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